It is known to provide axial and radial magnetic bearings in rotary machines having a vertical or horizontal rotor arrangement and to provide auxiliary mechanical bearings supporting the rotor in case of failure of the magnetic bearings, for example if the magnetic bearings are overloaded or if the electrical or electronic control system fails.
It is necessary to correctly balance the rotor of a rotary machine. Indeed, without correct balancing of the rotor, the rotary machine will not pass critical rotational speeds without contacting the auxiliary bearings.
It is known to balance the rotor of a rotary machine on a balancing facility.
In the case of a “rigid” rotor, there would be no rotor deformation due to unbalance forces increasing with speed. For a rigid rotor, the balancing can be performed at low speed, using a classical balancing facility.
The invention relates more to rotors having a “flexible” structure. In case of a rotor with a flexible structure and according to the rotor structure, there will be a deformation due to the unbalance forces increasing with speed. A flexible rotor which is operated above close to critical speeds must be rotated and balanced close to these critical speeds and above these critical speeds, close to the final speed.
High speed balancing facilities for such “critical”, flexible rotors are particularly expensive and necessitate many trial runs and the use of plurality of sensors. Furthermore, rotating a rotor of large diameter at very high speed on known balancing facilities can be particularly dangerous if the rotor is not correctly balanced.
Finally, vacuum is needed for such balancing facilities, which increases the costs of the balancing.
One aim of the present invention is to provide a balancing method adapted to balance at high speed a flexible rotor of a rotary machine directly when the rotor is mounted inside the rotary machine, without using a specific balancing facility.